In our copending application Ser. No. 894,376, filed Apr. 7, 1978, a system of this general type has been disclosed. As explained in that application, a large number of parisons can be produced by present-day injection-molding technology in as many mold cavities in an operating cycle of about 20 seconds. Upon discharge from the mold cavities, however, these parisons are still hot and therefore not sufficiently self-supporting to permit their transportation to an associated blow-molding unit by such means as an open conveyor without precooling.
In principle, the hot and therefore geometrically unstable parisons could be transferred without intermediate cooling from the injection cavities to the blow-molding cells by a carrier designed to hold them with close fit in individual pockets to prevent any objectionable deformation thereof. Since, however, the parisons are to be inflated in the blow-molding cells to a substantially larger diameter, the width of these cells greatly exceeds that of the cavities. To facilitate a direct transfer from the injection cavities to the blow cells, the cavities and the cells would have to form similar arrays with identical center-to-center spacing, yet this would require an injection mold of large area.
Such a direct transfer, if carried out under near-adiabatic conditions, would not only save time but also have the advantage of minimizing or even eliminating the reheating normally needed in a blow mold to facilitate the expansion of the parison by fluid pressure, The transformation of a parison into a completed workpiece such as a bottle by a blow-molding step, however, generally requires much less time (usually not more than about 6 to 8 seconds) than the injection-molding operation. Thus, a blow-molding unit synchronized with an injection-molding machine would operate at less than half its capacity.